Abstract: Nano-crystalline MnZn ferrites, Zn_xMn_1-xFe₂O4(x=0.2-0.4), were produced by the high energy milling method with high pure iron oxide prepared by chemical precipitation process as the starting material. Their structural properties were analyzed and characterized by means of X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The results showed that forma-tion of the nano-crystalline MnZn ferrites had two stages; the phase of ZnMn₂0₄ grew in the presintering first and then turned into Zn_0.2Mn_0.8Fe₂O₄ during the sintering process. The crystal growth mechanism was compendiously discussed.